“… Regarding the temporal attributes, it is noteworthy that even though Snodgrass had already identified and defined the relevance of the bi-temporal model as early as 1986, and then Worboys showed its feasibility in GIS, only 13 of the analysed models have taken into account both valid-time and transaction-time. Moreover, only two models, T/OOGDM (Becker et al 1996 and XSTUML (Price et al 2000, Price et al 2002, went one step further in considering a third temporal type for the modelling of additional temporal attributes, such as user-time or existence-time, to represent the availability of elements or the validity of a phenomenon (e.g., expiry date). However, these models do not consider this additional time variable far beyond its being a new attribute.…”